fn main() {
    println!("Hello, world!");
    let v:Vec<i32> = Vec::new();// 声明创建vector
    let v1 = vec![1,2,3];
    let third = v1[2];
    // 索引
    print!("索引获取{}",third);
    // get方法
    match v1.get(3) {
        Som(third) => println!("{}",third),
        None => println!("111111111111"),
    }
    print!("索引获取{}",v1[2]);
}
